As anyone who has created their own promotional material will tell you, there are two things you need to be aware of when creating something for commercial use:
1. Do you have the rights to use the photograph / picture?
2. Do you have the rights to use the font?
This second one might not be as obvious of a question, especially since most people will use the standard fonts present on their computer. However, if you're looking for a very "particular" font, make sure you have contacted the font artist and cleared it for "commercial" use. There are a lot out there that claim you can use them for "personal use", but anything you would use to sell something (like your book) is considered commercial.

Anyway, this was just a long, rambling intro for me to let you know of a few font resources on the internet I found while creating some promo material for my steampunk short story (needed the "Iron Man" font).
DaFont - http://www.dafont.com/
This website is quite incredible, as it lets you search fonts based on their style, but also on their licensing agreements (anywhere from "donationware" to "public domain"). They also have links to the font authors so you can easily contact them and purchase the rights to their fonts for your own work.
Pixel Sagas - http://www.pixelsagas.com/
One of the users on DaFont, Pixel Sagas has a lot of great fonts at a reasonable price (I paid $20 for a font that I can use for anything now).

Hugh Howey wrote:In everything you do as an author, work harder than anyone else around you. Want it more than you want anything else in life. Even if fortune doesn’t favor you, you’ll have zero regrets, and you’ll create something you’re proud of.